I actually got some nylon piston stops that are made by Stihl - they were very hard to find in Australia so I bought all 4 of them that the guy had in stock (Huonville Stihl Dealer, Tasmania - Top guy). Other Stihl dealers (as per usual) hadn't even heard of them! Excellent bits of gear.
However...
I also use rattle guns for clutches if I'm around a compressor
If you're running a 1/2" hose off a 40 cubic foot per minute 3 phase compressor with a rattle gun set for torquing up 450HP articulated John Deere Tractor wheel nuts you're bound to fu*k something up if using that setup on a chainsaw - particularly if you stuff it up and torque the nut the wrong way!
I've spoken to both Stihl and Husky dealers who swear by rattle guns for clutches and have also said they've seen more damage done by someone smashing a piston with the wrong type of piston stop (or even a sparkplug sized HSS drill bit), or by poking 1/2 a foot of nylon rope through the exhaust port and melting it in (if they've managed to cut it off to start with by managing to turn the piston over!). There is also the associated time saving factor of a properly setup and well used rattle gun in workshop conditions.
There is no way a properly set and competently used rattle gun could smash a clutch like it did in the first post. I do agree you'd have to be careful with alloy flywheel keys though.
Before everybody jumps up and down and has a dig at me just remember that some people are actually quite competent when using certain tools
and realise you can't use a rattle gun set on "I'll snap a truck axle mode" for an MS180 (or whatever) clutch.
Not trying to ruffle any feathers - just putting in my 2 cent's worth
Matt